Apparatus for determining finished roll density in a mill

Abstract

In the prior art it is known to determine the density of a roll of paper as it is being wound on a paper receiving roll. The determination is made each time the paper receiving roll makes a constant predetermined number of revolutions. Because the diameter of the paper on the paper receiving roll increases, there is an increasing length of paper added between successive determinations. This makes it more difficult to maintain a desired roll density by controlling various factors during winding. In addition, because the paper web is usually fed onto the roll at a constant rate, the time between successive density determinations increases. The system of the invention provides for an adjustment of the predetermined number of revolutions between density determinations. This number is decremented to provide, very approximately, the same time interval between successive determinations. This change in the number of revolutions of the paper receiving roll between predetermined calculations of roll density complicates the determinations made because the length of paper and change in diameter are both different between successive determinations. The apparatus detects these changes and incorporates the changes to get average values for use in calculations to provide a determination of roll density at intervals based on a substantially constant length of paper wound onto the paper receiving roll.

What we claim as new and desire to secure by Letters Patent of the United States of America is: 
     
       1. Apparatus for determining the density of a paper roll on a paper winding means comprising a paper receiving roll on said paper winding means for receiving a web of paper,   means for feeding said web of paper onto said paper receiving roll,   means for rotating said paper receiving roll to wind said web of paper onto said roll,   means for providing a first signal representing the rotation of said paper receiving roll,   counter means connected to said means for providing a first signal to receive said first signal and count the number of rotations of said paper receiving roll as represented by said first signal until a variable, preset count number N is reached for providing a second signal representing each count of N,   memory means connected to said counter means to store the number of counts of N, the number of counts being represented by K,   means to provide a third signal representing the length L of said web of paper wound on said paper receiving roll,   comparison means for comparing said third signal with a preselected value representing length and for providing a fourth signal when said third signal exceeds said preselected value,   means responsive to said fourth signal for decrementing N, and   means for determining paper roll density at intervals represented by K or a multiple thereof.   
     
     
       2. Apparatus for determining the density of a paper roll on a paper winding means comprising a paper receiving roll on said paper winding means for receiving a web of paper,   means for feeding said web of paper onto said paper receiving roll,   means for rotating said paper receiving roll to wind said web of paper onto said roll,   means to provide a first signal V respresenting the rotation of said paper receiving roll,   counter means connected to said means to provide a first signal for counting rotations of said paper receiving roll represented by said first signal to a variable count number N and for providing a second signal representing each count of N,   memory means connected to said counter means to store the number of counts of N represented as K,   means to provide a third signal representing the the length L of said web of paper wound on said paper receiving roll at successive counts represented by K,   comparison means for receiving said third signal, obtaining a difference value between two current successive lengths, comparing the difference value with a preselected value L c  representing a length, and for providing a fourth signal when the difference is equal to or greater than said preselected value L c ,   means responsive to said fourth signal for decrementing N,   means responsive to said third signal and said value for N for deriving a value for roll diameter D for successive readings of L and N according to   D=C L/N where C is a constant and for providing a fifth signal representing successive values of D for each successive K,   means for receiving said fifth signal and providing a first average values D(K-1/2) for the diameter of two successive value of D and a second average value D(K=1/2) for the diameter of the next two successive readings and providing a sixth signal representing successive average values,   means for receiving said sixth signal and determining a thickness t(K) according to ##EQU11## and for providing a seventh signal representing successive values for thickness, and   means for receiving said seventh signal and determining roll density d(K) for each thickness t(K) according to ##EQU12## where m is the paper basis weight.   
     
     
       3. Apparatus as defined in claim 2 in which said means for rotating said paper receiving roll comprises a pair of horizontally spaced parallel first and second drums, said paper receiving roll being aligned with and supported by said first and second drums, and means for driving said first drum to cause rotation of said paper receiving roll. 
     
     
       4. Apparatus as defined in claim 3 in which said means to provide a third signal comprises a pulse generator connected with said first drum for providing pulses representing rotation of said first drum, said web of paper engaging a portion of said first drum as it moves onto said paper receiving roll, the pulses being counted at successive counts as represented by K giving lengths represented by L(K), L(K+1), L(K+2) and so on. 
     
     
       5. Apparatus for determining the density d of a paper roll on a paper winding means at substantially regular intervals of time, comprising first and second, parallel, horizontally spaced drums,   a paper receiving roll supported by and aligned with said first and second drums,   means for rotating said first drum at a substantially constant rate,   means for feeding a web of a paper onto said first drum for engaging at least a portion of said first drum and extending onto said paper receiving roll to be wound onto said paper receiving roll as said first drum causes rotation of said paper receiving roll,   first measuring means for measuring the rotation of said paper receiving roll and providing a signal V representing the rotation,   second measuring means for measuring the rotation of said first drum and providing a signal Z representing the rotation,   first counter means connected to said first measuring means for receiving said signal V representing rotations of said paper receiving roll, counting rotations to a variable count number N, and providing a count signal K representing the number of counts,   memory means connected to said first counter means for storing the value for K, and the values V, Z and N for each K,   second counter means connected to said second measuring means and to said first counter means for receiving said signal Z and said signal K and providing a count signal L for each K, the count signal L representing length at the time of each successive signal K, and count signal L being stored in said memory means,   comparison means connected to said second counter means for determining a difference value L(K)-L(K-1) and for providing a change N signal when the difference value is greater than or equal to L c  where L c  is a preselected length value,   means connected to the comparison means for receiving the change N signal and decrementing the value N for the next calculation of density according to the equation N(K+2)=N(K+1)-1,   decision means initiated by the completion of each density calculation for determining if N has been decremented for the density calculation and in response to positive determination decrementing the count number N in the first counter means, and   density calculation means connected to said memory means for receiving said signals Z, V, N and L for each K and determining density d according to the equation: ##EQU13## where D D  is the diameter of said first drum m is the paper basis weight.